Originally Posted by CenValyCali (Post 4007431)

Thanks everyone for the ideas. Cali dude does one of those ends look like it would fit a rectangle?

Originally Posted by ray_mcavoy (Post 4016007)

Q-Jet carbs have a mechanical linkage connecting the primary (front) throttle blades to the rear (secondary) throttle blades. But there is a lockout mechanism that keeps the secondaries from opening if the choke isn't fully open. So make sure your choke mechanism is hooked up correctly and fully opening.

Q-Jet carbs also have secondary air doors above the secondary throttle blades. The air doors are spring loaded and only open based on engine airflow demand. So it's perfectly normal for the secondary air doors (at the top/rear of the carb) to stay closed or only open a tiny bit if you simply rev the engine with the trans in park/neutral.

Is the backfiring something new since the carb rebuild? Or was it doing that before too?

Originally Posted by CenValyCali (Post 4016344)

It's something new. I've never ran this carb on my truck before either. I found it at a junk yard and rebuilt it. I've tried to adjust mostly everything but have no ****ing clue what a good starting point is.

Originally Posted by ray_mcavoy (Post 4016377)

The rebuild kit should have included a paper with all the various adjustment specifications for all the carb #'s the kit fits. Look up your carb # (located on the driver side of the carb ... starts with a 170) on that paper and it'll give you all the settings for float height, choke adjustment, and such.

The paper was included with the kit but it was hard to understand. I still have it and will give it another shot. If I come up short I'll post my problems.


I assume you're meaning the idle mixture screws are 2 1/2 turns out since the jets are inside the carb and have a fixed size orifice. If that's the case, 2 1/2 turns should be enough to get the engine to start & run but might need some fine-tuning for a good idle. Adjusting these won't change the way the engine runs at higher speeds though.

That's exactly what I'm talking about. I'm guessing one is for air and the other is for fuel? Passenger would be fuel and driver side would be air?


Not sure what you're referring to here ... Idle speed screw over on the driver side of the carb?

I was told not to mess with that screw on the drivers side but if I wanted to mess with the idle I could turn the screw on the top of the carb, dead center in front of the buttlerflies.


Yes, the choke should be pretty much straight up & down when it's fully opened.

I'm thinking I didn't set the choke right and will work on that first.

There's a good carburetor troubleshooting chart at: http://www.recarbco.com/technical/newtrouble.html that you might find helpful.

Originally Posted by 85Bowtie (Post 4007327)

I thought the Quadra Junks were pre-set from the factory and had no provisions for adjusting the idle mixture without drilling something out or something funky like that.

Are you attempting a rebuild on the carb or the whole motor? If you're unsure of how to adjust the idle mixture on a Q-Jet you might as well forget about rebuilding it and just get you an Edelbrock.

Originally Posted by CenValyCali (Post 4016631)

That's exactly what I'm talking about. I'm guessing one is for air and the other is for fuel? Passenger would be fuel and driver side would be air?

Originally Posted by 68 TT (Post 4016918)

I know some Q-Jets had small caps put over the mixture adjustment screws to prevent people from tinkering with them. You can knock them out and get to the screws though. I had an emissions inspector try to fail a car once because the plugs were missing. I had to go to his supervisor and reason with him to get past it.